Calculation of NMR parameters for bridging oxygens in H_3T-O-T'H_3 linkages (T,T'=Al,Si,P), for oxygen in SiH_3O^{-}, SiH_3OH and SiH_3OMg^{+} and for bridging fluorine in H_3SiFSiH_3^{+}

Variations in the 17O nuclear quadrupole coupling constant, NQCC, and the 17O NMR shielding constant, σO, are evaluated for bridging oxygens in H3T-O-T'H3 linkages (with T, T'=Al, Si, P), and for nonbridging O in SiH3O‑, SiH3OH and SiH3OMg+ and the 19F NMR shielding constant, σF, is evaluated for bridging F in H3SiFSiH{3/‑}using Hartree-Fock methods with large, flexible Gaussian basis sets. Trends in 17O NQCC as a function of T and T' identity agree with experiment but the value for the Si-O-Al case is underestimated, indicative of neglected contributions from charge compensating cations. For H3SiOSiH3 the decrease in NQCC over the range from 180° to 140° is substantial but somewhat slower than the variation of -cos<Si-O-Si. The NQCC at bridging oxygen for R(Si-O)=1.607 Å and <Si-O-Si=140° interpolated from the calculations is 5.3 MHz, in good agreement with experiment. The calculated values of σSi and σO decrease as <Si-O-Si decreases, at a rate consistent with experiment. The calculations properly rank the σSi of the nonbridging oxygen of SiH3O‑ compared to the bridging oxygen of H3SiOSiH3 but the calculated σSi in H3SiOAlH{3/‑}is too large and σO too small, indicative of important contributions from counter ions. By contrast, σO for PH3OAlH3 compared to SiH3OSiH3 is consistent with experiment. In H3SiFSiH{3/+}(a model for bridging F in amorphous Si:H:F) the value of σSi is smaller and the NQCC at F is considerably larger than for H3SiF, suggesting distinctive 29Si and 19F NMR spectra for this species.